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T O P I C R E V I E W

moorouge

I'm intrigued by an unexplained reference to the Pioneer 10 and 11 flights.

This reference says that when these spacecraft were about the same distance from the Sun as the planet Uranus they began to slow down faster than expected. After analysis of the data in 2011 it was thought that this was due to the heat generated by the two craft creating pressure effects.

Does anyone have a more detailed explanation how this happens? And was the same effect observed with the two Voyager missions?

Jim Behling

The shape of the Pioneer spacecraft reflected/emitted more heat in one specific direction which led to a net propulsive force.

The effect is not seen on Voyager because the shape is different and the spacecraft were 3-axis stabilized which used thruster firings unlike Pioneer which was spin stabilized.

Look up Pioneer Anomaly or Effect.

Robert Pearlman

NASA's July 2012 release summarizing the findings, as published in the June 12 issue of Physical Review Letters, can be found here.

"The effect is something like when you're driving a car and the photons from your headlights are pushing you backward," said Slava Turyshev, the paper's lead author at NASA's Jet Propulsion Laboratory, Pasadena, Calif. "It is very subtle."

moorouge

If the effect quoted is correct then, presumably it means that one gets better mpg during the day when the headlights are off than at night when they are on. An interesting thought, though one that won't save one much money!!